This is Whiteline's adjustable rear swaybar for the 04+ WRX. Whiteline adjustable rear swaybars aid in reducing "roll" as well as helping with turn in and rotation of the car. Increasing rear swaybar size drastically changes the Impreza's handling balance for the better. These bars are three way adjustable with with one firmer and one softer setting. This allows you to fine tune the bar settings to your driving style as well as the other modifications you may make.
*Please note - the BSR33Z and the BSR36Z are the same bar. The difference is in the bushings. If you have any doubts about which one to get take a look at the chassis mount bushings on your car. If they have a flange on the outside of the strap for the bracket you want the BSR36 series. If the strap rolls over the sides of the bushing, and the bushing has no flange then you want the BSR33 series.